sirius.calc_a_noise

calc_a_noise_chunk(vis_shape, uvw, beam_model_map, beam_models, antenna1, antenna2, noise_parms, check_parms=True)[source]

Add noise to visibilities.

Parameters

  • vis_data_shape (float np.array, [4]) – Dimensions of visibility data [n_time, n_baseline, n_chan, n_pol].

  • uvw (float np.array, [n_time,n_baseline,3]) – Spatial frequency coordinates. Can be None if no autocorrelations are present.

  • beam_model_map (int np.array, [n_ant]) – Each element in beam_model_map is an index into beam_models.

  • beam_models (list) – List of beam models to use. Beam models can be any combination of function parameter dictionaries, image xr.Datasets or Zernike polynomial coefficient xr.Datasets.

  • antenna1 (np.array of int, [n_baseline]) – The indices of the first antenna in the baseline pairs. The _calc_baseline_indx_pair function in sirius._sirius_utils._array_utils can be used to calculate these values.

  • antenna2 (np.array of int, [n_baseline]) – The indices of the second antenna in the baseline pairs. The _calc_baseline_indx_pair function in sirius._sirius_utils._array_utils can be used to calculate these values.

  • noise_parms (dict) – Set various system parameters from which the thermal (ie, random additive) noise level will be calculated. See https://casadocs.readthedocs.io/en/stable/api/tt/casatools.simulator.html#casatools.simulator.simulator.setnoise.

  • noise_parms['mode'] (str, default='tsys-manual', options=['simplenoise','tsys-manual','tsys-atm']) – Currently only ‘tsys-manual’ is implemented.

  • noise_parms['t_atmos'] (, float, default = 250.0, Kelvin) – Temperature of atmosphere (mode=’tsys-manual’)

  • noise_parms['tau'] (float, default = 0.1) – Zenith Atmospheric Opacity (if tsys-manual). Currently the effect of Zenith Atmospheric Opacity (Tau) is not included in the noise modeling.

  • noise_parms['ant_efficiency'] (float, default=0.8) – Antenna efficiency.

  • noise_parms['spill_efficiency'] (float, default=0.85) – Forward spillover efficiency.

  • noise_parms['corr_efficiency'] (float, default=0.88) – Correlation efficiency.

  • noise_parms['t_receiver'] (float, default=50.0, Kelvin) – Receiver temp (ie, all non-atmospheric Tsys contributions).

  • noise_parms['t_ground'] (float, default=270.0, Kelvin) – Temperature of ground/spill.

  • noise_parms['t_cmb'] (float, default=2.725, Kelvin) – Cosmic microwave background temperature.

  • noise_parms['auto_corr'] (bool, default=False) – If True autocorrelations are also calculated.

  • noise_parms['freq_resolution'] (float, Hz) – Width of a single channel.

  • noise_parms['time_delta'] (float, s) – Integration time.

  • check_parms (bool) – Check input parameters and asign defaults.

Returns

  • noise (complex np.array, [n_time, n_baseline, n_chan, n_pol])

  • weight (float np.array, [n_time, n_baseline, n_pol])

  • sigma (float np.array, [n_time, n_baseline, n_pol])